I was thinking of going around the basement with a can of spray foam and
filling all the gaps in the ceiling (wire, pipe passages and heating ducts).
Then I realized that I have this big hole right in the middle for the
laundry chute. Even if I seal up the space between the floor and the duct
for the chute there is still a big hole that will allow air to flow. So I
forget, what is the purpose of sealing up all these holes again? Just
questioning myself here. Any ideas? Pro/Cons?

Thanks.